Hydraulic fluid mechanism



y 8, 1953 J. w. OVERBEKE 2,646,754

HYISRAULIC FLUID MECHANISM Filed Oct. 17, 1946 s'sheets-sneet 1 as J V 3/5 I T mmvrox.

6202/: v 288 JOHN WOVERBEKE.

BY 2 a W um. ATTOR s4 Jul 'zs, 1953 J. W. OVERBEKE HYDRAULIC FLUID MECHANISM Filed Oct. 17. 1946 9' 'Sheets-Sh'eet 2 INVENTOR.

JOHN W. OVERBEKE A T RNEYS July 28, 1953 J.-'W. OVERBEKE HYDRAULIC FLUID MECHANISM 9 Sheets-Sheet '3 Filed Oct 1' 1'1, -1946- m I mdm INVENTOR.

JOHN w. OVER BEKE A 7' TORNE Y5 July 28, 1953 J. WzOVERBEKE 2.646.754

HYDRAULIC FOJID MEcHANIm 4 Filed Oct. 17, 1946 9 Sh h 4 INVENTOR. JOHN W OVERBEKE BY M am A T RNEYS y 1953 J. w. OVERBEKE 2,646,754

HYDRAULIC FLUID MECHANISM Filed Oct. 17, 1946 9 Sheet$+$heefc 6 2 :LE g la/ I INVENTOR. JOHN W OVERBEKE 1 BY I A TTOI? EYS July 28, 1953 Filed Oct. 17, 1946 Fig/Z0 J. w. OVERB EKE 2,646,754

HipRAuLIcF Um-mmmsM INVENTOR. JOHN -W. OVERBEKE BY WM A T ORNE Y6 Patented July 28, 1953 UNITED STATES PATENT OFFICE HYDRAULIC FLUID MECHANISM John W. Overbeke, Cleveland, Ohio 7 Application October 17, 1946, Serial No. 703,733

27 Claims. 1

This invention relates to hydraulic mechanisms of the positive displacement type. The preferred embodiment, as described herein, is a pump adapted for use in high pressure hydraulic systems, but, as will be apparent to those skilled in the art, many features of the invention are capable of advantageous application to motors, metering devices, fiow dividers, and other hydraulic apparatus. However, for brevity in the specification the invention will be referred to as a pump. The embodiment which has been chosen for illustration of the principles of the invention is a high speed, high pressure pump particularly adapted for use in aircraft hydraulic systems by virture of its light weight, compactness, reliability and selfregulating features.

The objects of the invention include the provision of a pump, motor, or other fluid flow apparatus characterized by the following advantages:

compactness and light weight.

Adaptability to being driven by a variable speed prime mover such as an aircraft engine.

[Susceptibility of high speed operation.

Ability to operate at low speeds.

High output pressure.

Ability to operate with a high vacuum input.

Internal regulation of the output pressure, obviating the need for external relief valves and bypass circuits.v

The inclusion of a supercharging stage to insure proper flow of fluid to the displacement stage to prevent cavitation.

Provisions for lubrication of the Working parts of the pump.

Quick pump response to sudden increases in output flow demand.

A novel valving mechanism, providing highly effective sealing against leakage of fluid with a minimum of precision fitting of parts.

Means to balance the thrusts on the valve mechanism due to fluid pressure.

A construction facilitating the use of a forged casing and such as to minimize machining requirements for finishing the casing.

A positively driven track ring rotated with the cylinder block and receiving the piston thrusts.

Positive movement of the pistons in their intake strokes.

Quick self-priming action.

The provision of an apparatus incorporating these major objects and advantages involves many novel features of operation and arrangement, too numerous for further recital, which will be apparent to those skilled in the art from the following description.

By way of general description of the pump which has been devised to fulfill the objectives set out above, it is a development of a known type of pump having a fixed casing with a rotatable cylinder block therein, pistons operating in radial bores in the block engaging a track ring eccentric to the axis of the rotor and thereby being reciprocated. A centrifugal impeller mounted on the cylinder block acts as a supercharger in th pump intake. The track ring is pivoted so that its eccentricity may be varied, under the control of an automatic mechanism in the pump, for accommodation to conditions in which fiow from the pump is obstructed and to regulate the output pressure of the pump. Valving of flow of fluid through the pump is accomplished by a valve having one member rotatable with the cylinder block and a cooperating member fixed in the casing. Fluid flow devices of this general character are described in my co-pending applications for Hydraulic Fluid Mechanisms, Serial No. 637,699, filed December 28, 1945, now Patent No. 2,620,736; Serial No. 661,716, filed April 12, 1946, now Patent No. 2,552,449; Serial No. 677,714, filed June 19, 1946, now Patent No. 2,620,733; and Serial No. 687,399, filed July 31, 1946, now Patent No. 2,575,528. Certain features disclosed herein are disclosed and claimed in these co-pending applications.

Referring to the drawings:

Fig. 1 is an elevation view of the preferred embodiment of the invention as viewed from the intake and discharge end;

Fig. 2 is a plan view of the pump as viewed from below;

Fig. 3 is an elevation of the drive end of the p p;

Fig. 4 is a partial elevational View of the inner face of the casing end cap;

Fig. 5 is a sectional view of the casing end cap taken on the plane indicated by the line 5-5 in Fig. 3;

Fig. 6 is a sectional view of the pump taken in a substantially vertical plane through the axis of rotation of the cylinder block;

Fig. 7 is a sectional View of the pump casing and rotor taken in a generally horizontal plane passing through the rotor axis;

Fig. 8 is a cross sectional view of the pump;

Fig. 9 is a sectional view of the pump casing illustrating the inside of the casing end;

Figs. 10, 11, and 12 are views of the track ring;

Figs. 13, 14, and 15 are views of the intermediate member of an Oldham coupling;

Fig. 16 is a view of the rotor from the drive shaft end;

Fig. 17 is a side View of the rotor;

Fig. 18 is a view of the rotor and centrifugal impeller from the fluid flow end;

Fig. 19 is an enlarged sectional view of a portion of the pump illustrating the valve mechan1sm;

Figs. 20, 21 and 22 are views of the rotating valve plate;

Figs. 23;, 24. and 25 are views of. the stationary valve plate;

Fig. 26 is a fragmentary sectional view illustrating a modified structure for securing the end cap;

Fig. 27 is a longitudinal section of a bleed line sleeve incorporating a check valve;-

Fig. 28 is a perspective view ofapart of. the. check. valve of Fig. 2'7;

Fig. 29 is a cross section of a modifiedpressure control device, taken on the plane indicated by the line 29-49 in Fig. 30;

Fig.30- is: a longitudinal section of the. modified pressure control device, taken on the plane indicated by the line Elk-3.0 in Fig. 29; and

Fig..31 is a fragmentary sectional view taken on the planeindicated by the line. 3|-3i in Fig. 29.

General description The pump mechanism is 'housedin a casing 30 (Figs. 1 and 2) of circular cross section, tapering slightly toward the ends. The enclosure of the machine is completed by an end cap 31 (Figs. 2 and 3) provided witha flange for securing the pump to a prime mover. Power is taken from the prime mover through a coupling member 33 (Figs. 2 and 6) engaged with a rotor 35 which has two rows of radial cylinders in which pistons 35 (Figs. 6 and 3) are reciprocable. The outer ends of the pistons engage a track ring as freeiy rotatable in a guide ring 3?. The guide ring 3'1 is pivoted in the casing for movement about the axis ,38 to positions of varying eccentricity under the influence of the reactions of the pistons 35,

through the intake port 63 (Fig. 7) of the positive displacement stage, through the valve plates to the cylinders and back through the valve plates to the outlet port 44 (Figs. 7 and l).

Casing and. rotor mounting The pump casing is illustrated in Figs. .1 to 7. Iteiscontemplatedthat this casing be formed by forging, on account of the desirable characteristics of forged material, and the specific design shown herein is particularly adapted for forging, However, the casing may be produced by other operations such as casting. The casing at is constituted by a forged-cup having an outer shell portion 49 and a massive conical end portion 58 formed with threeebosses 5!, 52 and 53, equally spaced about-the central axis of the pump, for accommodation of the external fluid connections. The interior-of the .casing is finished for reception of the rotor, eccentric ring, valve mechanism, and so forth. The rotor 34 of the pump is formed with an annular extension 54 (Figs. 6 and 17) constituting-the innerrace of a needle bearing in which the rotoris supported. The rollers 55 of the bearing are guided by, the flanges 56v and 51 on the rotor and are retained in anouterrace 58 pressed into a bore 59 in the casing.

The drive end of the rotor is constituted by a shaft or extension 6i (Figs. '7 and 17) a portion $2 of which is dimensioned to fit a ball bearing 63 which supports the drive end of the rotor and serves as a thrust bearing to receive the end thrust. The outer race of the ball bearing 63 is received in a bore 66 in the end cap 35 of the casing. The end thrust of the outer race of the bea-rin is taken by a surface 61 (Figs. 4, 5 and 6). A washer 69 (Figs. 6 and "7) received against a shoulder NJ on the rotor transmits the thrust from the rotor to the inner race of the ball hearing- 63.3.

The mounting of the end cap 3! in the casing 36 is most clearly shown in Figs. 3 to 6 inclusive. Ari-externally; threaded mounting ring 13 is threaded into the casing 30 adjacent the open end thereof, and is locked into place by an Allen set screw 54 (Fig. 6) disposed outwardly from a recess l5 in the outer face of the .ring .l3,.into. engagement with'the casing. The. end cap 3% is main? tained in abutting relation with the ring '53 by a plurality of machinescrews i5 received incounterbored holes Ti in the end cap and in tapped openings 1% in the ring. Radial-alignment of the endplate 3! is attained by the fit of a fiangezlfl thereof within the .outer end of rthe.:machined inner bore of the casing.

The outer'portion of the end cap 3! isofrectangular outline, providing four outwardly ex-- tending ears 8% with holes.fititherethroughby means of which the pumpissecured to its prime mover. Alignment withthe prime mover .is assured by the machined radial outer face 83. .ofthe end cap and the shoulder 84 concentric with'the pump axis whichis adapted to be received in a matin bore of the prime mover.

Leakage between the casing and end. cap .is prevented by an O-ring or equivalent sealififi received in a circumferential recess 81' at the inner face of the end cap. Counterbores 38pmvide for the reception of O-rings 88 fitted over the end cap mounting bolts 16 to prevent leakage along the bolts. The end portion (Figs. 6 and 17) of the rotor shaftg which extends-almost to the outer face of the endcap, provides forithe mounting of a rotary shaft seal- M (Fig. 6). Since such shaft seals are well-lzriownarticles of commerce, and the invention isnotrestricted to the adaption of a particular type ofseal, no details of the seal are'shown herein;- The .-seal 9i is received in a bore 92 in the end cap. Leahage of oil along the outside surface of the seal is prevented by an O-ring 93 fitted in acounterbore 9:3 and retained in a-ring 95 screwedinto a threaded counterbore 9%, which' also' retainsthe seal 9!. The retainer fi-islocked in piece by a snap ring 95 retained ina groove 57 in the r-inner surface thereof and having-a projection 98 px,- tending through one of three notches 98a in the end of the retainer into one of four slots seem the face 83, extending from the-threaded. bore 96. Leakage of oil between the rotor-shaft-zfil and the shaft seal-8i is prevented by an O-ring h'li retained bya cup Hi2 fitted on the shaft. 6| between the rotary shaft seal and the ball bears ing. The 0-ring its is retained in a groovetl03 (Figs. '7 and 17) on the rotor shaft intermediate the portions 6! and-B2, andthe cup iti'isaetained against a shoulder HM.

Any oil accumulated in the interface between the prime mover andthe pump is collected inthe lower one of four circumferential recessesdflfi (Figs.-3, 5,-and '6) in the face BZi of the-pump end cap. Accumulated-oil is drained by: remoiving the appropriate one of pipe plugs IIII closing radial bores I08 connecting with the recesses I06. Preferably the inner face of the end cap 3I is forged with pockets I2I (Figs. 4 and 6) to reduce its weight. A circumferential groove I22 (Figs. 3 and 6) in the face of the end cap accommodates sealing wires for the mounting bolts I6.

The connection of the prime mover to the cylinder block 34 is effected by a coupling member 33 (Figs. 2 and 6) having a splined outer end portion III for reception in a splined socket of the prime mover, a reduced intermediate portion I I2 and a splined inner portion I I3 received in a splined socket H4 in the shaft portion of the cylinder block 34. The coupling member is retained by a snap ring II5 engaged behind a shoulder H6 at the mouth of the opening II4.

Cylinder block and track ring Proceeding now to a detailed description of the rotor or cylinder block, it is shown in the machine in Figs. 6, '7, and 8 and removed from the machine in Figs. 16, 17, and 18. As previously stated, the cylinder block 34 is mounted for rotation on a needle bearing 55 and a ball bearing 63 fixed in the casing assembly and is driven through its shaft extensions BI and 52. The rotor is of generally cylindrical form, and comprises a cylinder block portion I26 having two staggered rows of substantially radial cylinders. cylinders are shown in each row, but any convenient number may be provided. Flow of fluid to and from the cylinders is effected through seven passages I28 directed longitudinally of the cylinder block, each communicating with one cylinder in each row. As will be seen in Figs. 6 and 7, the passages I28 may be simply drilled into the block to a sufficient depth to intersect the cylinder bores I21. The inner ends of the cylinders of the two rows overlap as viewed from the end of the cylinder block, so that a single passage I28 may pass into a cylinder of each row, entering the cylinders of the right-hand row of Fig. 6 at the clockwise side of the cylinder as viewed in Fig. 8 and entering the cylinders of the other row at the opposite side. The pistons 35 are dimensioned for close sliding fit in the cylinders 31, except for the lower ends of the cylinders, which are recessed to a slightly larger diameter I29 to facilitate tooling operations.

Before proceeding to a description of the control of the flow of fluid to and from the pistons through the passages I28, the mechanism for effecting reciprocation of the pistons and certain details of the cylinder block will be described. The pistons are reciprocated by engagement with a track ring 36 (Figs. 6, 7, and 8) which is mounted for rotation about an axis eccentric to that of the cylinder block with the result that each piston is withdrawn from its cylinder during one half turn of the rotor and forced into the cylinder during the other half turn. The track ring 36 is rotated within a guide ring 31 which forms the outer race of a double-row needle bearing employing rollers I3I (Figs. 5 and 6). The outer surface of the track ring is formed with marginal flanges I32 and I33 and a medial flange I34 (Fig. 7) for guidance of the rollers and with ground bearing races I35 and I36 intermediate the flanges.

For reasons which are fully explained in my copending application Serial No. 687,399, filed July 31, 1946, for Hydraulic Fluid Mechanism, the track ring I34 is driven positively from the rotor shaft by an Oldham type coupling. The Oldham Seven coupling is constituted as follows: The rotor adjacent the cylinder block proper is milled away to form a rectangular portion I48 with flats I4I (Figs. 16 and 17). The flats I4I provide driving engagement with an intermediate coupling member I42 (Figs. 13 to 15) which in turn drives the track ring 3'! illustrated in Figs. 10 to 12 inclusive. The coupling member I42 is ring-shaped, with an ovate internal opening I43 for clearance over the cylindrical portion I44 of the cylinder block and with two outstanding segments I45, the opposed inner surfaces of which are spaced for sliding engagement on two of the flats MI. The

coupling member I42 is retained on the rotor between the shoulder I46 of the rotor and the thrust washer 69 (Fig. 6). Adjacent the projections I45, the coupling member I42 is formed with outstanding lugs I48 between which are milled or otherwise formed parallel-sided slots I49. The track ring 31 is provided with two diametrally opposed projections I5I proportioned for sliding engagement in the slots I49. As will readily be seen, the coupling thus constituted accommodates displacement between the axes of the rotor and track ring by radial sliding movement of the coupling member I42 with respect to the rotor and radial sliding movement of the lugs I5I in the slots I49 in quadrature thereto, and the track ring is always driven at the same angular velocity as the rotor.

We may now consider the mounting of the guide ring 37 in the casing, which is illustrated in Figs. 6, 7 and 8. The guide ring is hinged on a pivot pin 38 mounted in a bore I55 in the ring and parallel to the axis thereof. One end of the pivot pin is supported in a bore I56 in the end cap mounting ring I3, and its other end is supported in an aligned bore I51 in a ring I58 fitted into the casing. The ring I58, as will be seen, also. constitutes the scroll for the supercharging stage of the pump. Tapped holes I59 in the ends of the pivot pin facilitate its removal.

As the guide ring 3'! swings upwardly toward its position shown in Fig. 8, the eccentricity of the guide ring with respect to the rotor will be increased and thereby the stroke of the pistons and displacement of the pump will be correspondingly increased. The guide ring 3'! may swing downward to a position of zero eccentricity of the ring with respect to the rotor, in which case the displacement is zero. Upward movement of the ring 3! is limited by stop stud I6I threaded into a tapped hole I62 in the top of the casing and locked by a jam nut I63. By adjustment of the stop stud I6 I, the maximum displacement may be set at any desired point within the range of the pump. In operation, the reaction of the pistons on the ring due to the fluid pressures against the pistons tend to move the ring downward to the zero position of eccentricity, and therefore the output of the pump may be regulated by providing a control force to counter this tendency. The mechanism therefor will be described presently.

- The rings I3 and I58 are formed with radially extending ribs I65 (Figs. 5 and 7) which engage the edges of the guide ring and steady it against longitudinal movement or vibration. The rotor may be lightened by a drilling along its axis to form a cavity I61 (Fig. '7) which may be closed off by an aluminum cup I68 (Fig. 6) having a il'laanged end I69 engaging the bottom of the hole Under ordinary conditions of high speed operation, centrifugal force canv be depended upon to engage the pistons with the track ring. At

a a a fed to the-pump will force: thepistonsxoutzi. How

ever,'it is of grea-t value :to have za-ipump that:

will work-positivelyeven Ell -10W spee dsuand with a va'euum .in the feed lineln Tel-achieve this. result; there'must be armeans to dravmthe pistons: outward in the cylinders; Inssome' pumps, this: result is accomplished bytheruse ofsprings. In

the preferred embodiment oi-this. invention; :how

ever, the inner-surface ofxthatrack-ringaiifi :ist formed with inwardly. directed .marginalafianges- I15 amt-I16.(Figsxfiaand 12) .andthe:-.pistons are formed with: flanges 'sl TI- nearthe outerends of..-the.ipump,seven notches-z I81: may be/milled through. the 2 inwardly directed. portion of the flange 116 as. shownp. With the -flange'i'm thus cutaway; the track-ring fi can be slipped over the rotor with. the pistons? .-retracte 1 into- .the cylinders. Then the4pist0ns=-0futheeinnermost row can'be pulledaoum'and their flanges engaged in the flange H5 The flanges .ofr-the outer row of pistons are passed through the cut-away portions-swiof thee-flange H6, after which: the

ring. 3'?- i rotated sothat the flangesuof ithe.

pistons are retained .lintermediate the notches 81..- The: assembly can-be madewvi-th a-single notchii8 i,'byrotatingetherotor and ring relative to-each1othenandengaging the-pistons .one :at a time. The-.iing-B'i. is :maintainedin proper an? gular relation-.- to the rotor. :by the: .Oldham. cou-. pling.

The cylinders-I21 are boredat a:s1ightangle to the plane normal. to-thecylinder .blockaxis. In other Words, the=-tvvo-rows of cylinders are slightly,divergent.toward-their outer ends. The angle of. inclination oi-the cylinder to the. radius of=ther block may be-of the. order of two degrees. The inner surface iii-3 of the track .ringis a right circular cylinder. The inclination of thevpistons to the tracksring causes the pistons to. be. rotated in the. cylinders by the differentialiof. movement between the guide. ring .and the center. pistons. This feature.isnfullydescribed in .my above mentioned copending applicationNo.687 399 inlwhich the advantages thereof .are explain'ediand the angular relation of. 'tl1e--cy1inders.to the-track ring is claimed.

Valve mechanism The valve '.mechanism' of the pump ,is illustrated in: .and :19wto 1 25 inclusive. Basically,.the valve mechanism. isofa type-common in rotaryx-pumpsand motors, inwhich the cylindersrare': provided with individual ports which are in: commnnicationwith elongated kidney ports connected to .the.inlet---and .outlet lines: The elongated .ports are sodisposedtha-t the: individual cylinder ports are in contact-With the' intalre portl during the rotational period--.in

which-the piston iswithdrawn from the cylinder, and are in: contact: with the. outlet-: kidney part duringthe other-1 half of. the revolution; Valve meoha-nisms-ofi-this sort present many problems such as prevention of leakage, prevention of 1111.- due: friction and scoring of valve -plates,-.ancl-as surance ofdree flowi The -unbalanced-forces on the valve :parts edue to :thedifierence between inlet "and "outlet pressures-present another-prolzw lem. As will be seen from the valve mechanism embodied herein, many novel features have :been' incorporated herein to overcome difficulties 'pre viously experienced with this type of valve mechanism and to minimize the usual requirements of extreme precisionin machining andassembly.

of the parts of the valve mechanism. Thegeneral arrangement of the valve mechanism in" the pump is illustrated in Figs. 6, '7 and 19, the retating valve plate in Figs. 20 to 22 and the sta-' tionary valve plate in Figs. 23 to 25. The stationary valve plate 21' is of a simple disk-shaped outline, andis formed with two kidney-shaped ports, an inlet port 292 and an outlet port .li'lt symmetrically disposed relative to the pump axis. The central portions of the slots 2G2 and 203 are milled only partially throughthe valve plate, leaving strengthening ribs Zilito counteract the tendency of= fiuid pressure to expand :the valvepla'te. the finished plane inner surface 265 011 the-end portion 5?] of the casing, and is held in place byi a-machin'e bolt 2% (Fig.6) passing through an: The bolt 296is:

by a'pin Zfi'tiFigJfi) received in a bore-'illilrin' thecasing and a drilled hole .25! in the outer surface of the valve plate; The .normal'thrust due to fluidpressure tendsto maintain the valve plate Ziil in. close engagement witnthe casing. Leakage of fluid fromthe" ports 2&2 and 283 alon the outer face of .the valve plate is inhibited by c r-ings- .or equivalent seals retained in milled slotsi2i3 and iii in the outer face-of-the valve plate. surrounding the-ports. The intake port 282' opposes a kidney shaped passage 2| 5 in the casing and the-outlet'port 233 opposes a similar opening 2 iii in the casing.

Therotary'rvalve plate 2 i8 is formed" with seven ports therethrough, one for each of the fluid passagesiZBL The fluid passages 2H3 each compriseacircular opening 2283 boredinto the valve plate 258 from its inner face 22! andfian arcuate milled slot 222 formed in the-outer:surface223, which engages the stationaryvalve-platen The openings 22d and 222 are so proportioned so-as to be of approximately equal crosssectionalarea and they are joined by a tapered portion 223. The valve plate ii is rotated with thecylinder block by a construction similar to a-universal joint It comprises-a plug 225 (Fig; 1.9):fittedin a-bore 225 in the valve plate end of:the-rotor; andirotated positively Withthe cylinder-block byaa-key-ZZ'J. The plug 226 is formed With-a rounded head 228 projecting from the-cylinder block into .a centra1 opening 229 in the valve plate --2i8. The opening 223 is formed with diametrally opposed slots 233 which receive, for driving engagement, a pin 23! fixed transversely inthe head1228 or the plug 225. By meansoi this construction, the valve i plate 2|8 -=is con strained to rotate with the cylinder block-224 but may radapt any axial or angular rotation With the cylinder block necessary to conform to the valve plateZlil. l

The ports 202,- 2$3,and-222 are so proportioned that, except for ashort are at thedeadcenter positions of the pistons, thecylinders are in com munication with either the intake or exhaust port during. the entire rotation.

Thevalve plates are maintained in engagement with each other principallythrough the pressure .of thefluid through the agency :01? Pluhgers- .235

The valve plate is mountedzagainst.

face of the valve plate 9 freely slidable in the enlarged end portion 236 of the passages I28. Each plunger 235 is formed with a circumferential groove 231 in which is retained a sealing ring 238, and is formed with a central bore 239 for passage of the fluid, the bore 239 terminating in a shallow counterbore 240 in the outer end of the plunger and in a deeper oounterbore 2M in the inner end of the plunger. A compression spring 242 contained in the counterbore 2M and in engagement with the inner end of the enlargement 236 of the fluid passage normally urges the plunger 235 against the valve plate 218. Thus when the pump is not in operation the two valve plates are maintained lightly in engagement by the force of the springs 242. With the pump in operation, a relatively large force, tending to separate the valve plates, is exerted "by the confined fluid. The force tending to separate the valve plates Will obviously be proportional to the fluid pressure and will be principally exerted on the output or high pressure side of the valve plate. The force will vary slightly with the rotation of the pump, which varies the efiective area over which the force is exerted. In the pump described herein, the separating force is countered by exerting a force on the inner side of the valve plate 218 which is somewhat larger than the force tending to separate the plates and is distributed in approximately the same manner. The seating force in this invention is delivered by the pressure of the confined fluid against the annular inner faces of the plungers 235, which are so proportioned that their total area is slightly largerthan that of the fixed ports 202 and 203 plus such portions of the ports 222 as may be in communication with the fixed ports and overlying the unbroken sur- The force exerted on the valve plate 218 by the plungers will bear a definite relation to the separating force, will always be slightly greater, and will have approximately the same center of application. In this way, the proper seating force is obtained without unbalanced forces on any side of the valve plates.

The small amount of fluid which works from the ports onto the faces of the'valve plates will be collected in a shallow central recess 245 of the plate 20! or in a peripheral groove 246. The void space 245 is drained through two radial passages -1 in the valve plate and the groove 246 through a plurality of radial slots 248. The escaping fluid will lubricate the relatively moving faces of the plates.

Pressure control device We will now take up the manner in which fluid pressure is derived from the valve plate to actuate the hydraulic control mechanism (Figs. 1 and 8). While the pump has been described as running in one direction and having an intake side and outlet side of the valve plate 20l, actually the pump maybe operated in either direction, and either of the passages 202 and 203 may be the high pressure conduit. Means are incorporated in the valve plate 20l and its retaining bolt 206 to take off fluid under pressure from either of the passages 202 or 203 to balance partially the reaction of the pistons on the guide ring 31. The central hole 208 of the fixed valve plate communicates With the kidney-shaped ports 202 and 20-3 through two angularly disposed radial passages 252 and 253 (Fig. 19) which intersect the ports 262 and 203 at the face of the valve plate. The conduits 252 and 253 are formed with en- Ilarged inner bores 254 and .255, the endsof'fthe ,of its length from the ends.

enlargements forming seats for ball check valves 256 which are retained against dropping out of their seats by a spring ring 251 disposed in a groove 258 recessed in the hole 208. The retaining bolt 206 (Figs. '1 and 19) is centrally drilled to form an oil passage 26! communicating with the recess 258 by a cross drilled passage 262 in the bolt. A cross drilled passage 263 (Fig. '1) adjacent the head of the bolt 206 delivers fluid to an internal circumferential channel 264 in a collar 265 retained against the face of the casing by the bolt 206. O-ring or equivalent seals 266, 261, and 256 (Fig. '7) prevent escape of fluid along the bolt 206 or around the collar 265.

The collar 265 is welded or otherwise united to a pressure tube 210 (Figs. 1 and 2) which is sealed into the cylinder portion 21! (Fig. 8) of the control device 40. The cylinder 21l is disposed in a counterbored opening 212 in the casing wall 49 and is retained by a flanged nut 213 threaded on the inner end of the cylinder and bearing on the inner face of the casing. The fluid entering the cylinder 21l through the conduit 2'50 exerts pressure against a floating piston 214, the face of which engages a bearing ball 215 mounted in a semi-cylindrical groove 216 in the guide ring 31. A compression spring 211 maintains the plunger 214 in engagement with the ball 275. Seals 218 and 219 inhibit leakage of fluid along the inner and outer surfaces of the cylinder 21!. It will readily be seen that the ball checks 256 (Fig. 19) will close off the control passages from the low pressure inlet, but will permit passage of fluid thereinto from the outlet. The force of the fluid confined in the cylinder 21! urges the guide ring upward, opposing the piston reaction which tends to centralize the ring with the rotor. As will readily be seen, the force exerted by the plunger 214 is proportional to the output pressure of the pump. The pump input pressure, in the applications for which this type of control is contemplated, is normally very small relative to the output pressure. Therefore, the reaction of th pistons on the guide ring 231 is substantially proportional to the output pressure. Thus the difference between the moments of the two forces about the pivot of the pin 248 is substantially proportional to the pressure delivered by the pump. The area of the plunger 219 is such that the force exerted by it is slightly less than the resultant of the piston reactions.

The output pressure is limited and regulated by the leaf spring 39 (Figs. 6 and 8) which opposes the resultant hydraulic moment. The central portion of the spring 39 bears against a ball 28l in a depression 282 in the guid ring.

The ends of the spring are disposed under the flange. of the nut 213 and under a flange of a spring-retaining nut 283 held by a machine screw 282 provided with aseal 285. When the difference between the piston and plunger reactions pletely blocked, to bring the pump output to zero. The cutout pressure of the pump may be varied by adjusting studs 281 and 233 bearing against the spring approximately one eighth to one sixth The studs are locked in adjustment by nuts 289. By virtue of the controlling arrangement shown herein, the large portion of the force required to oppose the .piston reaction is delivered by the hydraulic plunger 214. The spring 39 may therefore be of relatively small tension and small size. The

spring 39 is of such form as to conformto the natural envelope of the pump, maintaining the compactness of the pump.

Supercharging stage We are now in a position to describe the centrifugal supercharging stage and generalarrangement of the casing and coupling for fluid flow through the centrifugal stage. The fluid intake of the pump is through a hexagon-headed bushing 4! (Fig. 6) threaded inside and outside, and screwed, into the bore 33! in the boss 53 of the end of the casing. The threaded bore 33! is disposed at a slight angle to the pump axis. A seal 332 received in a counterbore beneath the flange of the bushing 4! serves as a fluid seal. 1 From the inlet bushing 4|, fluid passes into a chamber 303 and then through two milled passages 304 (Figs. 6 and 9) to the interior of the casing adjacent the periphery of the valve plate 20 i. Fluid flows into a space between the peripheries of the valve plates 2M and 2l3 and the inner surface of the extension 54 of the rotor, which is the inlet chamber of the centrifugal impeller. The impeller is constituted by radial passages in the cylinder block and in an impeller ring 42 (Figs. 6 and 18) the ring being pressed or shrunk onto the rotor adjacent the flange its position being indicated by dot and dash lines in-Fig. 17. The impeller passages are preferably seven in number, spaced intermediate the fluid passages I23. The passages 33'! enter the end of the cylinder block adjacent the rotary valve plate and are-directed approximately 45 degrees to theaxis, and then radially through the cylinder block and communicate with aligned passages 338 in the impeller ring 336. The impeller ring 385 ismilled away on its inner face, that is, the one toward the pistons, forming recesses'between the passages 308.

The fluid from the impeller is discharged into an annular space 3H! defined by the. inner surface of the ring 558 mounted in the casing adjacent the periphery'of the impeller. and by a continuous semi-circular milled groove 3H in the inner face of the end of the pump casing (Figs. 6 and 9). Outflow of oil from the chamber 3E0 is effected through one of two deep milled pockets 3E2 and 3H3 (Figs. '7 and 9) extending axially into the casing end from the channel 3| I. The milled pockets tilt and 313 areangularly aligned with the fluid flow openings 43 and 44 respectively.

The openings 43 and 44, which are located approximately 120 degrees from the intake opening 4!, are bored into the bosses 52 and 5!. respectively. The outer openings 43 and'44 constitute the intake and. discharge ports. for the positive displacement stage of the pump and are connected to the valve plates through the passages 2i5 and 216. In order to adapt the pump for rotation in either direction, the openings 43 and 44 are adapted for interchangeable use as a means of connection between the supercharging stage and positive displacement stage, and as the discharge orifice of the. pump. 'The openings 43 and 44 are therefore bored out in identical fashion and are adapted to their specific functions by the cap 3L5 and sleeve 3l6-which are interchangeable, are formed with hexagon heads, and are adapted to be retained by the threaded portions 3 ll of the bores 43 and 44. Immediately within the threaded portion, a deep 'oflset recess 318 is bored in the side wall of each Q? he n the supercharger intake.

12 ings-43 and'44, breaking into the pockets 312 and 3| 3.

As the pump is set up, in Fig. 7, fluid flows from the supercharger into the space 363, through the conduit 3l2, the recess 3|3, the chamber 43, and the duct 2l5 into the valve mechanism. The operation of the valves and cylinder block has been described. The pocket 3H and recess 3!!! are blocked 01f from the outlet opening 44 of the pump by an extension 32! of the sleeve in which a sealing ring 322 is mounted. A sealing ring is also fitted in a counterbore 323 at the mouth of the opening 44. The discharge passage 2|3 from the positive displacement stage enters the opening 44 at the end thereof, and fluid flows through the sleeve 3H5 which is internally tapped at 325 for the reception of a fluid delivery conduit.

The cap M5 and the sealing ring 32'! substantially close off the outer opening of the cavity 43. The cap 3 i5 is formed, however, with a small orifice 328 therethrough, communicating with a tapped opening 323 which is adapted for reception of a pipe fitting. A pipe plug may be inserted in the opening 329 completely sealing the external opening of the cavity 43 if desired, or a low pressure return line may be connected to the cap 3 l 5 in which case a certain amount of low pressure oil from the centrifugal stage is bled from the pump, the amount of oil being governed by the size of the orifice 323. The purpose of bleeding oil in this manner is to provide a small circulation of oil to cool and lubricate the pump when, on account of blocking of flow in the high pressure discharge line, there is no discharge of oil from the positive displacement stage.

Sealing means are provided to inhibit circulation of oil from the supercharger back into the pump intake passage through the needle bearing 55. The periphery of the centrifugal impeller 42 is formed with a longitudinally extending flange. 333 immediately adjacent the periphery of the bearing race 58 extending into the annular recess 3 which, by centrifugal action, reduces thetendency of the fluid to flow between the impeller and the bearing race and forms a primary seal. A secondary seal is fitted between the end of the rotor and the inner face of the casing end, constituted by a flanged ring 334, the face of which is pressed against the end of the rotor by a ring 333 of synthetic rubber or the like seated in the flanged ring 334. A lip 336 (Fig. 6) forming an extension of the inner flange of the ring extends within the intake passage 304 to prevent rotation of the sealing ring.

It is inherent in the nature of pumps such as that described herein, that a certain amount of fluid will escape between the moving parts. This loss may be minimized by precise fitting of parts but can not be entirely eliminated. Provision is made in this pump to utilize the escaping oil to lubricate the pump and to scavenge excess oil from Within the casing. The valve plates 23! and 2 I 8 are lubricated by fluid escaping from the valve ports. Oil emerging from the inner face of the valve plates through the passages 24? and 243 in the valve plate 20! or escaping around the plungers 235 returns to the intake of the supercharging stage. Oil passing through the needle bearing 55 from the supercharger and through the primary and secondary seals also returns to Fluid passing between the pistons 35 and the cylinders is thrown against the inside of the track ring 33 by centrifugal force and through radial passages 336 in the track ring to the outer race, serving to lubricate the track casing.

F 13 ring needle bearings and finally escaping to the periphery of the casing. Fluid which escapes past the seal 1 ill on the drive shaft returns to the casing through passages 340 (Fig. 6) in the end cap and I in the end cap mounting ring to the periphery of the casing. Any excessive accumulation of oil in the casing will be thrown into the supercharger outlet passages by the impeller d2.

Modified end cap retaining structure Figure 26 illustrates a modified structure for the retention of the end cap 3! in the casing 33 which eliminates the use of a threaded retaining ring such as 13 (Figs. 5, 6 and 7). In the modified construction, a retaining ring 13a is employed which is similar to the form l3 previously described except that it is designed for retention by an expanding snap ring 360 retained in a groove 36I machined in the inner surface of the The retaining ring 1341 abuts against a small shoulder 352 in the casing during assembly and is held against movement out of the casing by the snap ring 350. The end cap 31 abuts against a shoulder 363 in the casing. Machine screws 16, as illustrated in Figures 3 and 5, pass through the end cap and are threaded into the retaining ring 13a. When the screws are tightened the end, cap is pulled tight against the shoulder 363 and the retaining ring against the snap ring 360.

Oil bleed line check value As previously described, the cap 3 I (Fig. 7) is designed for the connection of a bleed line to draw off a portion of the fluid which is passed through the supercharging stage of the pump. In certain applications, where there is a possibility of introduction of air into the feed line of the pump, and in which rapid self-priming of the pump is important, the presence of the vent connection to the cap 3H5 might delay priming because it would be possible to pump air in through the bleed line. To obviate this difiiculty in such applications as it may appear, a modified bleed line cap 3 iEa (Fig. 27) incorporating a check valve, may be employed. The plug MM is threaded into' the pump and sealed in the same manner as the plug 3l5 previously described.

boss 376 which locates the spring and prevents excessive movement of the ball 3? I. The retainer 313 is disposed in engagement with a shoulder 31! and is held in position by a snap ring 318. The cap 3| 5a is provided with an internally threaded opening 329 for the attachment of the bleed line.

Modified pressure regulator with a relief valve With the form of pressure regulator 40 (Fig. 8) previously described and with the check valves ,256 incorporated in the line through which fluid under pressure is fed to the cylinder Z'H, under some conditionsof operation, the check valves might impede the escape of oil from the cylinder i'll and thus undesirably delay the response of ,the pump to excessive output pressures. solution to this problem would be to eliminate the One regulator. the head portion 40! in alignment with the passage 44. as a motor the supercharging impeller and conanother or the valve plate 20! would have to be rotated degrees about its central axis.

The modified form of pressure regulator device illustrated in Figs. 29 to 31 is provided with a pressure relief valve to permit ready escape of the fluid from the cylinder 2'" in the event of excess load on the pump. The modified form of regulator comprises a head 40! and a cylinder portion 2', the cylinder being similar to that of the form previously described. The plunger 214 operates against the roll 215 and the regulating device is retained in place by a nut 213. The sealing rings 212 and 218 and the spring 211 are of the same form as in the previously described The pressure tube 210 is brazed into drilled passage 403, which is intersected by a passage 404 communicating with the cylinder 21!. A third passage 405 having a reduced end portion 406 likewise intersects the passage 493. The pressure relief valve disposed in the chamber 405 comprises a ball 40?, a plunger 408 and a compression spring 409 which is retained between the head of the plunger and an Allen set screw 4H] retained in the threaded outer portion 4 of the bore 405. The set screw M0 is locked by a second Allen set screw 4|2 having a turned portion 4E3 cooperating with an O-ring or similar seal M4 to prevent escape of fluid from the relief valve. In the event that excess pressure is developed within the cylinder 2', the ball 40'! is lifted from its seat, permitting fluid to escape from the cylinder through a diagonal passage M6 in the head MI. The outer end of the passage M5 is closed by a plug il'l brazed in place, Discharge of the escaping fluid is effected through the passage 418 formed by a short length of tub- 'ing brazed into the head 40! and entering a passage M9 drilled through the shell 49 of the pump.

A sealing ring 42!] disposed in a counterbore MI in the casing prevents leakage of fluid. As will be seen, if the pressure within the pump rises rapid- "ly, tending to drive the plunger 274 into the cylinder and fluid is unable to escape from the cylinder through the check valves in the fixed valve plate 2M, the fluid will lift the ball 491 in the relief valve and be discharged into the pump casing.

The relief valve 431 forms an additional means for regulating the cut-off point of the pump, since by adjusting the point of operation of this valve, the maximum pressure in the cylinder 21! "may be set to any desired value. The maximum pressure in the cylinder and the tension of the spring 39 (Fig. 8) determine the cut-off point :of the pump.

As has been stated, most of the structure disclosed herein as a pump is also adapted for use in hydraulic motors. In use as a motor, the supercharger is unnecessary, and may be cut out by inserting sleeves 3H5 in both passage 43 and Of course, in a machine designed nectingpassages therefor may be omitted. The

variable-volume feature would ordinarily be 115 ,nmitteddn a motor, and may be in a pump, by l-flxingitheguide' ring 31in the casin andomitting .the mechanisms which control the position v of E the :ring.

Although the foregoing description is necessarily: of a detailed character, in order that the invention may be completely set forth, it is to be .understood that the specific terminology is not .intended to be restrictive or confining, and that various-rearrangements of parts and modifications of detail may be resorted to without departing fromthe scope or spirit of the invention as herein claimed.

I claim:

"1.= In a fluid displacement machine, a rotatable cylinder block having radially directed cylinder openings therein, pistons in the cylinders, an an- -nular member surrounding the cylinder block and engaged by the pistons, the member being ;mounted for motion with respect to the cylinder block so as to vary the displacement of the machine by varying the eccentricity of the central axis of the member with respect to the axis of rotation of the cylinder block, the effect of fluid :pressure in the cylinder block normally tending to reduce the displacement to zero, opposed means responsive to fluid pressure within the machine tending to move the member in an opposite direction, the means tending to decrease displacement having the greater effect, and initially stressed resilient means increasingly stressed as thedisplacement is decreased.

,2. In a fluid displacement machine, a rotatable cylinder block having radially directed cylinder openings therein, pistons in the cylinders, an an- =nular member surrounding the cylinder block and engaged by the pistons, the member being rmountecl'formotion with respect to the cylinder 'block'so as to vary the displacement of the machine byvarying the eccentricity of the central axis of the member with respect to the axis of rotation of the cylinder block, the effect of fluid pressure in the cylinder block normally tending to reduce the displacement to zero, opposed means responsive to fluid pressure within the machine tending to move the member in an opposite direction, the means tending to decrease "displacement having the greater effect, the differential effect of the opposed means being substantially less than the effect of either means, and initially stressed resilient means increasingly stressed as the displacement is decreased.

3. In combination with a fluid displacement machine having radially directed cylinders, pistons therein, and control means for effecting reciprocation of the pistons, the control means being movable from a position in which the pistons operate through a full stroke to a cutoff position in which the pistons are stationary with respect to the cylinders, and in which the reactions of the pistons on the control means urge it toward its cutoff position; regulating means constantly urging the control means toward its full-stroke position comprising a device responsive to fluid pressures within the pump and a stressed resilient member operatively engaging the control means to provide a constant biasing force opposing the reactions of the pistons upon the control means whereby the control means is :caused to assume a cut-off position relatively rapidly when the difference between the actions of the control means and the regulating means exceeds that of the stressed member.

54. In combination with a fluid displacement :machinehavlng radially directed cylinders, pistons therein,.and 'control'means for effecting reciprocation of the pistons, the control means being movable from a position in which the pistons operate through a full stroke to a cutoff position in which the pistons are stationary with respect to the cylinders, and in which the reactions of the pistonson the control means urge it toward its cutoff position; regulating means constantly urging the control means toward its full-stroke position comprising a device responsive 'to the pump output pressure and a stressed resilient member operatively engaging the control means to provide a constant biasing force opposing the reactions of the pistons upon the control.meansrwhereby the control means is caused to assume a cut-off position relatively rapidly when the difierence between the actions of the control means and the regulating means exceeds that of thestressed member.

5.. In combination with a fluid displacement machine having cylinders, pistons therein, and control means for effecting reciprocation of the pistons, the control means being movable from a position inwhich the pistons operate through a full stroke to a cutoff position in which'the pistons are stationary withrespect to the cylinders, and in'wh-ich the reaction of the pistons on' the control means urge it toward its cutoff position; regulating means constantly urging the control means toward its full-stroke position comprising a device responsive to the pump output pressure and comprising a flat spring and means to vary the initial stress of the flat spring.

6. In combination with a fluid displacement machine having cylinders, pistons therein, and control means for effecting reciprocation of the pistons, the control means being movable from a position in which the pistons operate through a full stroke to a cutoff position in which the pistons are stationary with respect to the cylinders, and in which the reactions of the pistons on the control means urge it toward its cutoff position; regulating means urging the control means toward its full-stroke position comprising a fiat spring, a part on the control means engaging the midpoint of the spring, abutments at the ends of the spring, and adjustable means between the abutments and midpoint for biasing the spring toward the control means.

7. In combination with a fluid displacement machine having cylinders, pistons therein, and control means for effecting reciprocation of the pistons, the control means being movable from a position in which the pistons operate through a full stroke to a cutoff position in which the pistons are stationary with respect to the cylinders, and in which the reactions of the pistons on the control means urge it toward its cutoff position, regulating means urging the control means toward its full-stroke position comprising a fiuid-pressure-responsive device engaging the control means, fluid connections between the said device and the inlet and outlet passages respectively, of the machine, and check valves in the said fluid connections soarranged that the deviceis isolated from the passage under lower pressure and actuated by fluid from the passage of higher pressure.

8. 'In-a fluid displacement machine, a cylindrical casing, a cylinder block of the radial-cylinder type rotatable in the casing, pistons in the block, a track ring engaging the heads of the pistons, a guidering in which the track ring is supported, a pivotal mounting for the guide ring whereby it mayzmove to vary the eccentricity. of

the track ring'with respect tothe cylinder block, a hydraulic cylinder radial to the casing, a piston in the cylinder engaging the guide ring for rotation thereof about its mounting, a flat spring disposed circumferentially of the casing between the guide ring and casing, abutments in the casing for the spring, a part on the ring engaging the spring intermediate the abutments, and means movable radially of the casing engaging the spring to vary the tension thereof.

9. In a fluid displacement machine, a casing, a cylinder block of the radial-cylinder, type rotatable in the casing, pistons in the block,.a track ring engaging the heads of the pistons, a mounting for the track ring whereby. it may move to vary the eccentricity of the track ring with respect to the cylinder block, a hydraulic cylinder radial to the casing, a piston in the cylinder connected to move the track ring, a fiat spring disposed between the track ring and casing, abutments in the casing for the spring, a part connected to the ring engaging the spring intermediate the abutments, and means movable radially of the casingengaging the spring to vary the tension thereof.

l0. In a fluid displacement machine, a cylindrical casing, a cylinder block of theradial-cylinder type rotatable in the casing, pistons in the block, a track ring engaging the heads of the pistons, a guide ring. in which the track ring is n supported, a mounting for the guide ring Whereby it may move to vary the eccentricity of the track ring with respect to the cylinder block, a hydraulic cylinder radial to the casing, a piston in the cylinder engaging the guide ring for movement thereof, a flat spring disposed circumferentially of the casing between the'guide ring and casing, abutments in the casing for the spring, and a part on the ring engaging the spring intermediate the abutments.

11. In a fluid displacement machine, a cylindrical casing, a cylinder block of the radial-cylinder type rotatable in the casing, pistons. in the block, a track ring engaging the heads of the pistons, a guide ring in which the track ring is supported, a pivotal mounting for the guide ring whereby it may move to vary the eccentricityof the track ring with respect to the cylinder block, and a hydraulic device responsive to pressures Within the cylinder block engaging the guide ring for rotation thereof about itsmounting.

12. In a fluid displacement machine, a casing, a cylinder block of the radial-cylinder type rotatable. inthecasing, pistons in the block, a ring eccentric to the cylinder block for effecting reciprocation of the. pistons, a. pivotal mounting for the ring whereby it may move tovary the eccentricity of the ring relative to the cylinder block, a hydraulic actuator engaging the ring for rotation thereof about its mounting, a flat spring disposed circumferentially and externally of the ring, abutments in the casing for the spring, a part on the ring engaging the spring intermediate the abutments, and means movable radially of the casing. engaging the spring to vary the tension thereof.

13. In a fluid displacement machine, a casing, a cylinder block of the radial-cylinder type rotatabl'e in. the casing, pistons in the block, a ring eccentric to the cylinder block for effecting reciprocation of the pistons-,- a mounting for the ring whereby it may move to vary the eccentricity of the ring relative to the cylinderblock, a hydraulic actuator engaging the ring for movement thereof, a flat spring disposed circumfer- .entially and externally of the ring, abutments in the casing for the spring, and a part on the ring engaging. the spring intermediate the abutments.

i l. In a fluid displacement machine, a casing, a cylinder block" of the radial-cylinder type rotatalolein the casing, pistons in the block, a track ring for. reciprocating the pistons, a mounting for-the track ring whereby it may move to vary the eccentricity of the track ring with respect to the cylinder block, a hydraulic cylinder radial .to-the casing, a piston in the cylinder connected to move the track ring, a flat spring disposed between; the track ring and casing, abutments in the casing; for the-springa part connected to the ring engaging. the spring intermediate the-abutments, and means movable radially of the casing engaging the.- spring to vary the tension thereof.

15..In a fluid flow device, a rotary cylinder block; flow control means comprising a valve plate rotating with the cylinder block and a fixed valve plate, the valve plates being in face-toface contact; fluid flow passages from the cylinders being aligned with ports in the rotating valve plate; means for approximately balancing forces exerted by fluid pressure on the face of the rotating valve plate comprising a plunger in each passage engaging the rotating valve. plate and formed with an axial bore, the. bore being recessed adjacent the valve plate end of the plunger, the plunger rim being disposed around the corresponding port; and a driving connection of the universal joint type between the cylinder block and the rotating valve plate.

16. In a. fluid flow device, a rotary cylinder block; flow control means comprising, a valve plate rotating with the cylinder block'andta-fixed valve plate, the valve plates being. in face-toface contact; fluid flow passages from the cylinders being aligned with ports in the rotating valve plate; and means for approximately balancing forces exerted by fluid pressure. on the face of the rotating valve plate comprising. a plunger in each passage engaging the rotating valve plate and formed with an axial bore, the bore being recessed adjacent the valve plate end of the plunger, the plunger rim being disposed around the corresponding port.

17. In a fluid flow device, a rotary cylinder block; flow control means comprising a valve plate rotating with the cylinder block and a fixed valve plate, the valve plates being in face-t0- face contact; fluid flow' passages; from the cylinders being aligned with portsin the rotating valve plate; means for. approximately balancing forces exerted by fluid pressure on the face of the rotating valve plate comprising a plunger in each passage engaging the rotating valve plate and formed with an axial bore, the plunger rim being disposed around the corresponding port; and a driving connection of'the universal joint type between the cylinder block and'the rotating valve plate.

18.A= hydraulic device comprising a casing having inlet and outlet ports, a cylinder block mounted for rotation in the casing, the cylinder block having radially directed cylinder openings, pistons in the openings, and valve means for successively connecting the cylinder openings to the inlet port and then to the outlet port upon rotation of the cylinder block, a first annular member surrounding the cylinder block, a pivotal mounting for said first annular member supported by the casing, a second annular member mounted for coaxial rotation with respect to the 19 first member and adapted to rotate in synchronism with the cylinder block and engaging the pistons, rotation of the annular members about the pivotal mounting serving to vary the eccentricity of the common axis of the members with respect to the axis of rotation of the cylinder block, means responsive to the pressure of fluid in the cylinder openings connected to the outlet port, the said means being supported by said casing and being adapted to rotate the annular members upon the mounting to increase the eccentricity of the axes in response to changes in fluid pressure, and biasing means disposed between the casing and the first annular member to provide a constant rotational force tending to increase the eccentricity of the axes.

19. The invention in accordance with claim 18, said fluid pressure responsive means comprising a piston connected to the first annular member.'

20. The invention in accordance with claim 18, said fluid pressure responsive means comprising a piston connected to the first annular member and the component of force tending to change the eccentricity of the axes of the annular members with respect to the axis of the cylinder block due to the piston being less than the component of force due to the actions of the pistons in the cylinder openings upon the second annular member.

21. The invention in accordance with claim 18, said biasing means comprising spring means supported by the casing and engaging the first annular member.

22. The invention in accordance with claim 18, the component of force tending to increase the eccentricity of the axes of the annular members with respect to the'axis of the cylinder block due to the fluid pressure responsive means being less than the component of force tending to decrease the eccentricity due to the action of the pistons in the cylinder openings on the second annular ring and the component of force due to the biasing means being greater than the first two named forces. 1

23. A hydraulic device comprising a casing having a valve end and a drive end, a cylinder block mounted for rotation in the casing, the cylinder block having radially directed cylinder openings, valve means comprising a first means associated with the casing and rotatable means associated with the cylinder block, the valve means being rotationally symmetric about the axis of rotation of the cylinder block and defining a valve face generally normal to the axis of rotation of the block, the valve members having cooperating parts and passageways for conducting fluid to and from the cylinder openings as the cylinder block rotates, pistons in the cylinder openings, the pistons normally being urged radially outward of the cylinder openings by fluid in the openings, an annular member surrounding the cylinder block mounted for rotation about an axis eccentric to the axis of rotation of the cylinder block, whereby during one-half cycle of rotation, the ring forces the pistons into the cylinder and during the other half cycle of rotation, the ring normally limits the outward. movement of the pistons, a coupling device connected to the cylinder block and to the annular member for positively driving the'member with the cylinder block, and means providing interengagement between the ring and pistons to withdraw the pistons from the cylinder in the event of non-action of fluid forces normally acting thereon.

24. The invention in accordance with claim 23, said last named means comprising a flange on the piston and an inwardly directed flange on the annular member for engaging the flange on the piston.

25. The invention in accordance with claim 23, said last named means comprising an inwardly directed flange on the annular member having a peripheral groove therein and a flange on the piston received in the groove.

26. A hydraulic device comprising a casing having a valve end and a drive end, a cylinder block mounted for rotation in the casing, the cylinder block having radially directed cylinder openings, valve means comprising a first means associated with the casing and rotatable means associated with the cylinder block, the valve means being rotationally symmetric about the axis of rotation of the cylinder block and defining a valve face generally normal to the axis of rotation of the block, the valve members having cooperating ports and passageways for conducting fluid to and from the cylinder openings as the cylinder block rotates, pistons in the cylinder openings, the pistons normally being urged radially outward of the cylinder openings by fluid in the openings, an annular member surrounding the cylinder block mounted for rotation about an axis eccentric to the axis of rotation of the cylinder block, whereby during one-half cycle of rotation, the ring forces the piston into the cylinder and during the other half cycle of rotation, the ring normally limits the outward movement of the pistons, fluid pressure means responsive to fluid in the passageways and connected between said casing and said annular member and increasing the eccentricity of the axis of the annular member with respect to the axis of the cylinder block in response to increasing pressure, a coupling device connected to the cylinder block and to the annular member for positively driving the member with the cylinder block, and means providing interengagement between the ring and pistons to withdraw the pistons from the cylinder in the event of nonaction of fluid forces normally acting thereon.

27. The invention in accordance with claim 26, said last named means comprising a flange on the piston and an inwardly directed flange on the annular member for engaging the flange on the piston.

JOHN W. OVERBEKE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,006,880 Benedek July 2, 1935 2,074,068 Ferris Mar. 16, 1937 2,129,828 Dunn Sept. 13, 1938 2,129,886 Syrovy Sept. 13, 1938 2,130,299 Ernst Sept. 13, 1938 2,164,888 Sassen et al. July 4, 1939 2,273,468 Ferris Feb. 17, 1942 2,293,692 Wylie Aug. 18, 1942 2,299,233 Hoffer Oct. 20, 1942 2,299,234 Snader et a1 "Oct. 20, 1942 2,324,524 Mercier July 20, 1943 2,407,013 Ifield Sept. 3, 1946 2,426,588 Benedek Sept. 2, 1947 2,429,011 Wylie Oct. 14, 1947 

